The present invention relates to an apparatus for the frontal introduction of marking strips during the formation of stacks of sheets, such as paper sheets.
When depositing sheets, in particular sheets of paper, in a sheet stacking device it is customary to place marking strips between counted quantities of sheets, referred to as "reams", to facilitate the identification and removal of individual reams, for instance for separately packing these reams. The reams are normally fed to the packing machine frontally away from the stack, for which purpose the respective stack, lying on a lift table, is placed againt a fixed vertical butt plate of the machine. For the transfer of each ream into the packing machine, the operator introduces an "air knife" into the stack under the respective marking strip and thereby pushes the ream lying thereon into the packing machine. This procedure presupposes that the marking strips appear on the front of the stack opposite the butt plate, although the feeding of sheets to the stack inside the stacking device occurs frontally. Considering that the stacks usually lie on a pallet flush with a front side and that, for technological reasons, this front side--the same which later will apply against the butt plate of the packing machine--is the one from which the sheets were supplied to the stack, the marking strips must be introduced into the stack on the side opposite the front side.
In the apparatus of the type known from Belgian Pat. No. 778,307, the marking strip inserting tongue moves in above the stack approximately horizontally, then drops onto the stack by its free end, in order to form below the following sheet a wedge-shaped gap, into which the marking strip enters. It then rises again into a substantially horizontal position in order then to withdraw from the stack profile without interfering with the injected strip. Although this known apparatus functions satisfactorily, it is unusable where, as is presently customary, sheet feeding to the stack occurs under guide belts that pass over the stack since these guide belts leave no room for the respective tongue movement inside the stack profile. If the height of the gap formed by the tongue in the stack is reduced to a few millimeters, as would be necessary in this case, there is a danger that, on the one hand, the marking strip may miss the gap which is no longer exactly controllable and, on the other hand, that the withdrawing tongue may entrain and draw back with it a properly injected marking strip.